The name of this species, the black spotted salamander, is derived from the fact it has black spots scattered across the dorsal (or upper) surfaces and sides of the body and tail. It is thought to be closely related to another top 100 EDGE plethodontid: the Veracruz green salamander. This species was once relatively common. Although no accurate population data exist, it is now known to be very rare, if not extinct, and was last seen in the mid-1980s. Most of the habitat of this species has either disappeared or has been severely degraded as a result of logging, agriculture, and expanding human settlements.

Urgent Conservation Actions

Protection of the remaining habitat at the two known occupied sites for this species is urgently required.

The Plethodontidae is by far the largest family of salamanders, comprising nearly 70% of all living species. In total there are 378 known plethodontids divided between four subfamilies and 24 genera. The plethodontids are united by the fact that they do not possess lungs and breathe entirely through their skin and mouth lining. They are often referred to as the lungless salamanders, although they are thought to have evolved from highly aquatic, lunged ancestors in the streams of the Appalachian Mountains in eastern North America. The earliest plethodontids were hypothesised to have lost their lungs because individuals with reduced, or absent lungs were less likely to float away in the swift mountain streams where they lived. The vast majority of other salamanders possess lungs, making the lungless salamanders an unusual and fascinating group of animals.

They are thought to have diverged from all other amphibian species 145 million years ago at the boundary between the Jurassic and Cretaceous periods. They are as different from all other amphibian lineages as wombats are from whales, evolving at a time when dinosaurs were still dominant. Overall, plethodontids are the most evolutionarily advanced salamanders, so it may at first appear odd that they should have lost their lungs, which are one of the most basic features of all vertebrates living on land. Lacking lungs and being dependent on their skin for respiration places a size restriction on these salamanders because large animals have a relatively small surface area of skin compared to their body’s volume, and have greater difficulty in supplying their body tissues with oxygen compared to smaller animals (which have a large surface area to volume ratio). The long, slender form of the lungless salamanders maximises the surface area available for gas exchange, and some species grow to lengths of over 300 mm.

Plethodontid salamanders occupy a great diversity of habitats, ranging from strictly aquatic to strictly terrestrial, exploring niches as diverse as caves, trees, mountain streams, and they are also found burrowing through the earth. Dependence on their skin for breathing places limitations on where and how lungless salamanders can live. Their skin must be kept moist at all times in order for oxygen to be taken up by the blood in capillaries beneath the skin. This means plethodontids are either confined to humid areas, or must find damp hiding places and only emerge in wet weather, typically at night. The life of a lungless salamander in less humid areas, like Europe and temperate North America, therefore comprises brief periods of activity interspersed with inactive phases that are often very long. They are able to survive the periods of inactivity because they have a very low metabolic rate and low energy requirements. Able to store much of what they eat as fat, they do not need to feed very often.

A further adaptation, present among many species of the lungless salamander subfamilies named “Plethodontinae” (from East and West North America) and “Bolitoglossinae” (from tropical Central and South America), is “direct development”. This is a method of amphibian development where the larval stage (e.g. the tadpole stage in a frog’s life history) has been eliminated. Early development takes place in eggs, which may be laid in moist places away from water, and the young hatch out as miniature adults. The well known amphibian metamorphosis, most commonly appreciated in the transition from tadpole to adult frog, does not occur outside of the egg. This means that certain lungless salamanders in these two subfamilies may live away from water bodies, allowing them to expand their ranges to new areas.

The history and characteristics of the lungless salamanders go some way to explaining their range. They are mostly found in the New World, where they are widely distributed in eastern and western North America, as well as Central and South America. However, continental drift over millions of years has also brought them to the Old World, where they are found in parts of Europe (e.g. Sardinia) and Korea. The existence of the Korean crevice salamander was unknown until 2005, when its discovery was a shock to science, indicating a long history of lungless salamanders in Asia. This is the only known species in Asia, suggesting that the rate of species generation in this part of the world is very low, especially compared to the huge radiation of lungless salamander species in the New World.

Comprising 50 known species, the genus Pseudoeurycea (commonly known as the “false brook salamanders”) is one of the largest genera in the Plethodontidae family, second only to the Bolitoglossa genus (the “mushroomtongue salamanders” – 93 known species). The false brook salamanders are present within the subfamily “Bolitoglossinae” (from Central and South America) and its members are very wide ranging in size, with some of the smallest and largest lungless salamanders included (total lengths from about 65 mm to 325 mm).

The false brook salamanders have recently been reorganised and expanded to absorb a number of other genera that are now considered to fit within the Pseudoeurycea genus. The taxonomy of these salamanders may not be finally resolved just yet, but it is known that the whole group diverged from all other salamanders in the Late Eocene period, at least 34 million years ago. This is around the same time that humans and monkeys shared a common ancestor.

The black spotted salamander is thought to be closely related to another top 100 EDGE plethodontid: the Veracruz green salamander.

Description

The black spotted salamander, like all lungless salamanders in the Bolitoglossinae subfamily, possesses a slender body, long tail and prominent eyes. A distinctive feature of the plethodontid family is a narrow groove (the nasolabial groove) running from each nostril to the upper lip: its function is to carry waterborne odours from the ground into the nasal cavity. Another curious trait of the lungless salamanders are mental (from the Latin “mentum”, meaning chin) glands. These are modified mucus glands and release pheromones, which are chemicals produced by an animal to influence the behaviour of other members of its species, often with regard to breeding receptivity. Mental glands are sometimes visible in males as raised bumps below their lower lip.

Lungless salamanders are very small to medium in size, usually measuring between 25 to 250 mm from the tip of the nose to the end of the tail, which salamanders retain throughout their life. They are unusual among the salamanders in that some species can detach from their tail as a predator-defence mechanism (also known as tail or caudal autotomy). It is therefore not unusual to see individuls missing part or all of their tail, which they may regenerate later. Lungless salamanders may have bold patterns on their skin as adults, or they may have a colouration more similar to their environment to aid camouflage. They have well-developed “costal” grooves (successive vertical grooves in the skin along the sides of the body), generally numbering between 12-15. Their limbs are slender and often have largely or completely webbed digits. Species, like the black spotted salamander, in the genus Pseudoeurycea (the “false brook salamanders”) are very similar in form to those in the genera Chiropterotriton (the “splayfoot salamanders”) and Bolitoglossa (the “mushroom-tongue salamanders”).

The black spotted salamander is a medium-sized species, reaching a total length of around 120 mm, with the long tail accounting for over half of this measurement (about 65 mm). The tail is constricted at its base and thirteen “costal” grooves are present along the sides of the body, in addition to 33 grooves along either side of the tail. The limbs are well developed, with digits that are broadly flattened and webbed at their base. The colouration of this species is a fairly uniform grey-black or dark lavender on the dorsal (or upper) surface. The ventral surface (or underside) is a few shades lighter, and silvery flecks may be visible on the chin and sometimes also on the head and body. Black spots appear scattered across the dorsal (or upper) surfaces and sides of the body and tail

Ecology

Like other false brook salamanders, the black spotted salamander is probably active all year round and mating is thought to occur throughout the year. Some species in this genus are known to display courtship rituals. The pheromone releasing mental gland in males plays an important role in mating to influence the receptivity of females. During amplexus (the mating embrace), the male clasps the female with both his arms and legs, and rubs pheromones across the female’s snout. Fertilisation is internal and eggs will generally be laid at the beginning of the dry season in November. Female false brook salamanders have been found to guard the eggs throughout their development in many species, often in special hides, until hatching occurs at the beginning of the rainy season. Little is known about the black spotted salamander but it is understood that direct development of the young occurs within the eggs and they hatch as miniature adults. This whole process is independent of a water body, making this a truly terrestrial (or land-dwelling) species. It lives in bromeliads, which are neotropical plants with overlapping leaves that provide damp or water-filled hiding places. The eggs of this species are laid on strings and the embryos have gills, but these are lost before the young hatch.

False brook salamanders are well adapted for moving around their habitat and have prehensile tails, meaning they can use their flexible tail as a fifth limb to grip with and hang from. This may prove particularly useful in arboreal (or tree-dwelling) species like the black spotted salamander. False brook salamanders may at first appear very vulnerable to predators but a number of defense mechanisms have been found among the members of this genus. These include: noxious skin secretions; poisonous gland on the back of the head (parotoid glands); warning colours on the skin of the back (also termed aposematic colouration) or camouflage colouration; and caudal autotomy (tail detachment). Behaviourally, false brook salamanders have been found to orchestrate many defensive methods, including immobile posture, coiling and flipping of the body, tail undulation displays, and biting.

Habitat

The black spotted salamander is arboreal (or tree-dwelling) in montane tropical forest or cloud forest, where it is found living in bromeliads. Bromeliads are a common type of plant from the Neotropics which possess overlapping leaves that may trap water and organic debris, providing a habitat for numerous species of invertebrate, amphibian and other creatures. They are often found growing on other plants, especially trees. These bromeliad species are termed “epiphytic” bromeliads, from the Greek “epi” meaning upon and “phyton” meaning plant. Dwarf brook salamanders are only found within the larger tank-forming bromeliads, which contain a number of substantial pools of water (or minute aquaria) between their leaves.

Distribution

The black spotted salamander occurs in only two sites in southern Veracruz, Mexico: the peak of Cerro Chicahuaxtla, Cuatlalpan, at an altitude of 1,600 metres above sea level; and at 1,200-1,300 metres above sea level on Volcán San Martín. It is likely, although unproven, that this form actually consists of two separate species, one in each site.

The black spotted salamander was once relatively common. Although no accurate population data exist for this species, it is now known to be very rare, if not extinct, and was last seen in the mid-1980s.

Population Trend

The IUCN Red List of Threatened Species indicates that the black spotted salamander’s total population size is generally in decline.

Status

Listed as Critically Endangered on the IUCN Red List of threatened Species because its extent of occurrence is less than 100 km sq., all individuals are in a single location, and there is continuing decline in the extent and quality of its habitat, and in the number of mature individuals, in east-central Veracruz, Mexico.

Threats

Most of the habitat of this species has either disappeared or has been severely degraded as a result of logging, agriculture, and expanding human settlements.

Conservation Underway

The black spotted salamander is not known from any protected areas, although it is protected under the category Pr (Special Protection) by the Government of Mexico.

Establish spatial knowledge of the distribution and occurrence of some of the threatened species in Mexico.

Screen individuals and other amphibians in these areas for the presence of chytrid fungus.

Increase the capacity in Mexico for the long term conservation of these species

Conservation Proposed

Protection of the remaining habitat at the two known occupied sites for this species is urgently needed. Survey work is also needed to ascertain whether the species survives in the wild at either site, and any resulting discoveries can inform a conservation action plan for the black spotted salamander.

In addition to conserving wild habitat for this species, the IUCN Technical Guidelines for the Management of Ex situ Populations, part of the IUCN Red List of Threatened Species, recommend that all Critically Endangered species should have an ex situ population managed to guard against the extinction of the species. An ex situ population is ideally a breeding colony of a species maintained outside of its natural habitat, giving rise to individuals from that species that are sheltered from problems associated with their situation in the wild. This can be located within the species’ range or in a foreign country that has the facilities to support a captive breeding programme for that species. Further investigation is therefore required into the possibility of establishing a captive breeding programme for the black spotted salamander. Captive animals could then be a source of new individuals to repopulate any restored habitat.